After you clear security in San Juan, the next thing you encounter is a large duty-free store; in fact, you literally can't miss it, because you have to walk through it in order to go to the gates. Here's a link to the store's liquor offerings (not attesting to when it was last updated), https://sanjuan.shopdutyfree.com/en/liquor, but it shows Jack Daniels and Woodford Reserve as available. Easy enough to just grab a botte there and carry it onto the plane with you.